1. Field of the Invention
This invention relates in general to systems designed to use treated timber for landscape purposes, and more specifically to systems utilizing modular timber units with interconnecting end portions secured with braces and angled spikes and periodic deadman joints to provide overall support.
2. Description of the Prior Art
While the use of treated timber for landscape purposes such as retaining walls or boxed gardens has been known for a considerable period of time, the most common and popular method for installing such timber has remained relatively unchanged and unimproved. Generally, this method requires the timber to be cut at a specific length and many times at angles of less than 90 degrees. Because these cuts are made at the landscape site, they are usually made with a chain saw, a tool which is both dangerous and difficult to operate for the novice. Next, the timber is drilled so that large spikes, lag bolts or other type fasteners can be driven through one piece and into the next piece immediately below for stability. The ultimate problem with this cumbersome process is that it provides for relatively weak and unstable joints, and over a period of time, pressure exerted on these joints will simply cause them to pull apart.
Retaining wall and planter construction systems using modular components are disclosed in U.S. Pat. Nos. 3,343,301 and 4,869,018. While the devices disclosed in these patents utilize a shoulder and socket system to connect the modular units, both rely upon the earth to rigidly secure such joints along with the relative positioning of each unit. Vertically aligned pins used to connect these joints do not, in and of themselves, prevent rotational movement by the units.
A landscaping system utilizing modular timber units is manufactured by Thompson Industries, Inc. Essentially, these units or timbers interconnect with each other through the use of rabbet-type joints with each unit having a male and female end. Once the units are an interlocking position, a wooden dowel may be passed through holes contained in the ends of the adjoining timbers and thus provide some stability to the interlocking joint. However, as with the systems disclosed in the '301 and '018 patents, this dowel does not prevent rotational movement between the interconnected members. Thus, some other stabilizing element is required, such as the earth that is being retained.